The molecular structure of selected cell membranes and other marcomolecular specimens will be investigated by new techniques of high resolution electron microscopy. In this work, images are obtained of unfixed, unstained, hydrated specimens. The electron exposure used is kept below the critical dose for radiation damage effects. Spatial averaging of images of crystalline specimens can provide high resolution structural information under these conditions. The structural studies in this program will also take advantage of the decrease in radiation damage that occurs at low temperature, and of the improved detector-characteristics of "nuclear track" photographic emulsions.